BATTERY AND ELIMINATOR

Radio Record, Volume I, Issue 42, 4 May 1928, Page 13

BATTERY AND ELIMINATOR

oe F the ordinary listener were asked for criticisr-: on the present standard valve set. for broadcast reception he would. probably concentrate on the batteries. . The filament accumulator is troublesome because it requires periodical recharging and, in addition, exhibits a preverse tendency to run down just when it is most wanted. As regards high tension, the dhi'ycell battery is a recurring charge on the wireless budget, and after the first few weeks of service usually develops artificial "atmospherics" of its own. , The remedy seems to lie in the use of eliminator units which are adapted to derive all the current and voitage necessary to run a multi-valve set direct from the electric lighting mains. At the present time the ideal combination is probably to be found in the indirectly-heated cathode type of valve in which special "false" filaments are fed directly from the mains, with a special eliminator unit for supplying the plate voltage from the same source. _ Eliminator units designed to produce both filament and plate supply from the mains are, of course, available, but the indirectly-heated valve has the advantage that it is peculiarly free from noise, whilst owing to the fact that no current flows through the actual cathode, the latter is maintained at the sagne potential throughout its length and thus operates at maximum efficiency. High-tension Elimixators With regard to high-tension eliminators, it ‘is generally found that the alternating-current type gives more satisfactory results, all round. than the D.C. type, "hough, of course, the latter is cheaper to install. In the former type the A.C. transformer completely separates the eliminator units from the outside mains, and thus protects the receiving set from variations in load and corresponding fluctuations in voltage.